Hypertension Overview 9/10/2014

Question 1

T/F: HTN is a disease

Answer 1

false: it is a syndrome that encompasses a large group of disorders

Question 2

HTN is fundamentally a disorder of regulation of ________.

Answer 2

Systemic Vascular Resistance

Question 3

HTN is believed to be the end product of the interaction of what 3 concepts?

Answer 3

-hereditary, environment, behavior

Question 4

3 broad manifestations of HTN

Answer 4

1. SAP is regulated at a sustained abnormally high level
2. abnormal regulation of Na and body fluid metabolism
3. abnormal fibrosis (deposition of collagen) in tissues

Question 5

2 broad categories of hypertension

Answer 5

1. primary (essential HTN) which can be resistance HTN or compliance hypertension (stiff pipes seen in old age)
2. secondary HTN

Question 6

3 big areas of detrimental consequences of HTN

Answer 6

1. LV: generates a higher systolic P which increases LV wall stress in systole, causes LV hypertrophy (concentric), generalized fibrosis in myocardium that decreases LV diastolic compliance=impaired relaxation (diastolic dysfunction)
2. arterial system: increase wall stress in SA system; arterial vascular disease (aneurysms, accelerates atherosclerosis), arteriolar disease: obliterative destruction which increases SVR even more
3. Kidney: due to arteriolar destruction which further decreases ability to excrete Na

Question 7

What is the most common cause of chronic renal failure?

Answer 7

-HTN causing obliteration of systemic arterioles including those in the kidney

Question 8

4 main clinical consequences of HTN

Answer 8

1. cardiac dysfunction due to progressive LVH and fibrosis: CHF
2. accelerated atherosclerotic and aneurysmal disease of large-medium systemic arteries: MI, stroke, aneurysms increase
3. progressive destruction of systemic arterials= increase SVR
4. renal dysfunction secondary to renal destruction of arterioles: contributes to excess Na retention

Question 9

Worldwide prevalence of HTN and the excess death rate people with it carry

Answer 9

• 1 billion people

- about 1% increase per year

Question 10

CV morbidities associated with HTN

Answer 10

• CAD, Peripheral vascular disease, stroke, CHF

- all go up as severity of either systolic or diastolic HTN increases

Question 11

Blood pressure and age

Answer 11

-thought to be normal that there is an age related increase with BP; systolic more so than diastolic and this means pulse pressure increases with age

Question 12

Problems with the definition of hypertension

Answer 12

• epi: continuum of BP values in the population, disorder is so prevalent that it may appear normal, tendency for increase with age
• morbidity: continuum of frequency of morbidity with BP

Question 13

When it comes to BP, ______ is always better!

Answer 13

-lower

Question 14

Normal, preHTN, stage 1 and stage 2 HTN cut offs

Answer 14

Normal: / 160 or >/100

Question 15

Primary vs Secondary HTN

Answer 15

primary: no identifiable cause linked to a particular organ system
secondary: caused by a disorder of 1 of the arterial pressure regulatory mechanisms: kidney disease, adrenal disease, CNS disease, drug intake

Question 16

3 mechanisms which should prevent HTN but malfunction

Answer 16

1. baroR reflex: reset to higher threshold
2. pressure-natruiresis in kidney does not function appropriately
3. RAAS: does not shut off renin as it should–some pts have ACE mutations

Question 17

In what societies do we not see an increase in HTN prevalence with age?

Answer 17

-societies with low sodium diets–Yanomano Indians of SA

Question 18

Impact of dietary sodium intake on HTN prevalence

Answer 18

• 1 tsp (<2 g/d is idea) but only 3.3% of world does this

- for each increase of salt intake (per g) BP increases more.

Question 19

Dahl R and S rats and the significance

Answer 19

• R rats remained normotensive at high Na diet
• S rates developed severe HTN and died early on; had less renal Na output at any level of arterial inflow pressure
• impact of genetics

Question 20

The Rice Diet

Answer 20

• diet virtually free of sodium fed to severely HTN patients
• produced dramatic reductions of BP with resolution of many abnormalities
• showed the beneficial effect of Na restriction

Question 21

Factors other than Na intake known to influence prevalence of HTN

Answer 21

• environmental stress: HTN more prevalent in urban than rural pops; genetically predisposed individuals have a more pronounced vasoC response to stress than normals (seen in renovasculature)
  2. obesity
  3. physical inactivity: exercise reduces BP
  4. alcohol consumption

Question 22

Resistance vs Compliance HTN

Answer 22

• resistance: fundamental abnormalities is abnormal regulation of vascular resistance. SVR is elevated. Systolic, diastolic, and MAP are all elevated, pulse pressure is modestly elevated. Typical arterial P is 150/100
• compliance: issue = decreased great vessel compliance. SVR is normal or slightly elevated. Systolic P is elevated, diastolic is normal or low, MAP is modestly elevated. Pulse pressure is greatly elevated (due in part to inc pulse wave velocity). typical arterial pressure is 170/60

Question 23

Consequences of compliance HTN

Answer 23

• severe LV P overload
• causes severe LVH (decreased LV diastolic compliance, causing diastolic HF– HFpEF)
• accelerated vascular disease: aortic aneurysms, Cerebrovascular dz

Question 24

“Vicious Cycle” in HTN

Answer 24

• initial effects: increase total body Na, increase SVR
• subsequent effects: destroy systemic arterioles (inc SVR), lose functioning renal mass, tissue fibrosis (cannot excrete Na)
• consequences: progressive increase in SVR, progressive loss of renal function and ability to excrete Na, increase CV load (heart and arterial system), changes in LV systolic and diastolic properties

Question 25

So what causes essential HTN?

Answer 25

• probably not a single disorder, or monogenic

- any explanatory mechanism must take into account heredity, environmental factors, Na relationship

Question 26

Mechanism of essential HTN

Answer 26

• issue with too much Na that the kidney cannot excrete.
• this raises intraV blood volume and causes release of natriuretic hormone that inhibits the Na/K ATPase.
• this causes Na to build in cells which turns on the Na-Ca2+ exchanger which removes Na but increase intracellular Calcium–> vasoconstriction and increase SVR

Question 27

What is Natriuretic Hormone?

Answer 27

-Not yet identified but believed to be a Na/K ATPase inhibitor important in developmental of essential HTN

Question 28

Can anything be done in addition to picking a healthier, low Na diet?

Answer 28

Yes, weight loss amplifies these effects.

Question 29

Renal Sympathetic Hyperactivity

Answer 29

• perhaps another possible mechanistic constributor to essential HTN
• pts with HTN have increase afferent and efferent renal sympathetic nerve activity
• denervation not seen to be better than sham

Question 30

What is likely the fuel that drives the evolution of HTN in genetically susceptible individuals?

Answer 30

-dietary Na intake